In the building industry, cutting openings for doors, windows, ventilation ducts, stairways, foundations, etc. through objects such as walls, roofs, and floors are frequent operations. Objects of this type often are thick and they typically consist of reinforced concrete, stone, brick, masonry, metal, wallboard, panelling, and similar building materials, or various composite building materials. Various techniques are employed for performing the cutting operations. Known mechanical working machines are used, such as chain saw machines or ring cutter machines, that have various advantages as well as disadvantages.
Chain saw machines employed for cutting hard materials, such as stone and concrete are diamond-tipped. Typically these machines have a guide bar and a saw chain of a considerable length, which makes it possible to cut/penetrate thick objects. Among the drawbacks of such machines is that the wear of the links of the saw chain is severe when cutting materials of the mentioned type. Such wear shortens the use life of the saw chain. Wear shortening of use life is a serious drawback, especially because diamond tipped saw chains are very expensive. Another drawback is that very powerful engines are required for this machines type. Further, also the guide bar and the drive wheels are subjected to wear because of the slurry that is generated during the work, especially because the chain slides in a groove in the guide bar and because only water is used as a lubricant. The guide bar and the drive wheel therefore also frequently need to be replaced.
As far as cutting machines that have rotating cutting or sawing disks of a conventional type are concerned, the maximal cutting depth is limited to less than half the diameter of the used cutting or sawing blade. This limited cutting depth is due to the fact that the rotation axis of the disk (blade), i.e. its spindle, always is longer than widths of the kerf (cut) that the blade makes in the object being cut. When larger objects are to be cut (e.g., when making openings in thick walls, roofs or floors), machines having very large, rotating blades need to be used. However, larger blades and the associated powerful driving motors required to rotate larger blades result in an increase in weight and a decrease in portability/manoeuvrability. Conventional machines that are used for cutting and/or sawing very thick objects therefore are not hand-held machines. Vice versa, hand-held cutting machines of conventional type can be used only for working comparatively thin objects. A machine belonging to this category is shown, e.g., in U.S. Pat. No. 3,583,106.
Cutting machines of the ring saw type (see for example, U.S. Pat. No. 4,646,607), has an off-center drive of the cutter blade. As such, there is a lack of a hindering central spindle, which in turn allows cutting to greater depths than half the diameter of the saw blade. However, the diameter of hand-held machines of the ring saw type is limited because of the weight of the machine, which will be considerably large if the blade is large, especially as big blades also need to be comparatively thick in order to be of sufficient strength. As is the case for other conventional cutting machines, the necessary drive power is increased in relation to the diameter of the blade, which further increases the total weight of the machine. When the blade is diamond-tipped, the costs for the diamond tipping is also increased very much if the diameter as well as the thickness of the blade are increased. Therefore, there are technical as well as economical limitations of the blade size, which in turn restrict the feasibility of this type of machines as far as the thickness of the object to be worked (i.e., cut) is concerned.
A so-called flat sawing machine is a special type of cutting machine. An example of this type of machine is shown in U.S. Pat. No. 5,887,579. The saw blade of a machine of this type has one side that is flat, i.e. it is void of projecting parts. On the opposite side there is a spindle, which is driven by a driving assembly at the side of the saw blade. Machines of this type are used in order to make sawing, e.g., into a wall at a corner where two walls intersect, possible. In such a situation, the flat side of the saw blade is applied close to one of the walls to permit the saw blade to cut into the other wall in the corner. It is to be noted that such a machine, however, can only be used for cutting walls, which are thinner than slightly less than half the diameter of the saw/cutting blade.
Further it is known through WO 01/23157 to dig into an object, more particularly into a rock formation desired to be mined in connection with a quarrying process, wherein two slots are cut into the rock at a distance from one another. In a subsequent operation, the rock material between the slots is crushed. The tools in this case are rotated about a joint axle having axle spindles, which project laterally from the outer sides of the outer tools of the tool assembly. The axle spindles set a limit for the penetration depth. Alternatively, a very broad trench may be achieved through several working operations, which allows working deeper into the rock formation, so that finally a ditch-like trench having stair-stepped or sloping walls is achieved.
In light of the above background there is a long felt need of machines of improved performance. Specifically there is a need to cut deeper than what has been possible to do according to the prior art, employing disk shaped, rotatable tools having a certain diameter. It is particularly desirable to make it easy to handle the machine, not only during the cutting or corresponding operation but also, e.g. in connection with exchange of replacement parts, in the first place of the tools. It is also desirable to reduce the number of machine components that must handled in connection with a change of tools. For these and other reasons, it is desirable to be able to use tool units that include a tool and a driving member as will be described in the following disclosure and to adapt the cutting machine to such tool units.